4 ms·

The performance of this website seems a little low. I'm noticing a lot of lag when I scroll that I don't notice on other sites... Is it because of the lib?

• delluminatus 11y ago
  No (edit: kinda). It looks like the site calls setState() on the root React component every time the scroll event is fired. For those not familiar with React, setState() is a function that is used to update mutable state, and it is not a very cheap function, because it propagates the state through all child components, re-renders some virtual DOM, and potentially also causes actual DOM reflowing. Calling this in the scroll handler is what causes the noticeable delay. edit: it seems like the lib itself does also call setState on scroll [0]. I don't think this is the source of the issue on the site itself, which has additional scroll handlers (for the magic non-scrolling sidebar), but it could cause similar performance problems, depending on how many child components are in your Context. [0]: https://github.com/casesandberg/react-context/blob/master/src/context.js#L162 https://github.com/casesandberg/react-context/blob/master/sr...
  • seivan 11y ago
    Out of curiosity how did you find that out? I've been looking for a decent debugging workflow for React.
    • delluminatus 11y ago
      Sorry to say, it's nothing React-specific. I understand that there is a React Developer Tools addon for Chrome that might be of interest [0]. As for me, I just turned on Javascript CPU profiling in Firefox Developer Tools, scrolled a bit, and checked what JS calls were causing the slowdown. Because the unminified source for the website is available on Github, you can quickly find and examine the functions' code directly [1]. [0]: https://chrome.google.com/webstore/detail/react-developer-tools/fmkadmapgofadopljbjfkapdkoienihi?hl=en https://chrome.google.com/webstore/detail/react-developer-to... [1]: https://github.com/casesandberg/react-context/blob/gh-pages/docs/components/home/HomeBody.jsx#L96 https://github.com/casesandberg/react-context/blob/gh-pages/...
      • seivan 11y ago
        Thanks. I've been spending too much on the Rails and iOS stack that I've lost track on proper front end tools and workflows. Appreciate it.
• Hovertruck 11y ago
  Potentially. This lib is going to call setState on every scroll event, which is triggered multiple times every time you scroll up or down the page. Traditionally you would debounce a scroll handler like this.
• JoshTriplett 11y ago
  Probably; JavaScript scroll handlers often incur a major performance penalty.